Thank you Alexis and Kaushal. I might mislead you.

I am writing some short articles which includes a lot of Math formula. So I
include LaTeX command here and there like $A \subset B$. Most symbol
display OK when exporting to HTML. But the \subsetneqq not. Same article,
Html couldn't handle $\subsetneqq$ and display "Undefined control sequence
\subsetneqq" in final render. But display in PDF output correctly.

I guess this problem relates to MathJax and did a little googling  last day
but didn't find the solution.

[image: 2017-12-03 06-38-24 的屏幕截图.png]


Kaushal Modi <kaushal.modi@gmail.com>于2017年12月2日周六 上午11:49写道：

> On Fri, Dec 1, 2017 at 9:56 PM Alexis <flexibeast@gmail.com> wrote:
>
>> \subsetneqq is a TeX command, not something that's part of Org.
>
>
> Try emailing emacs-orgmode@gnu.org and see if this is something that can
> be added to Org entities. I have seen that Org entities includes many of
> the LaTeX supported symbols with the same syntax for many cases.
>
> You can do M-x org-entities-help and see the symbols currently supported.
>
>
>> To
>> add
>> that symbol, which i believe is Unicode SUBSET OF ABOVE NOT EQUAL
>> TO,
>> you can either enter it directly into a buffer by typing:
>>
>>     C-x 8 RET SUBSET OF ABOVE NOT EQUAL TO
>>
>> or by typing:
>>
>>     &#x2ACB;
>>
>> which is an HTML character entity referring to that character.
>>
>
> That's another way :)
>
> Just to add a bit more to that.. if you are able to copy the symbol from
> somewhere to emacs and you want to know what it's called (like, SUBSET OF
> ABOVE NOT EQUAL TO in this case), put the cursor on that symbol and do C-u
> C-x =.
> --
>
> Kaushal Modi
>